1. Field of the Invention
The present invention relates to a modular weighting system for recreational and professional underwater divers that permits the regulation of overall buoyancy and also allows for a specific distribution of weight over a diver's body to maintain the desired degree of horizontal trim.
2. Description of the Related Art
Scuba (Self Contained Underwater Breathing Apparatus) divers, whether recreational or professional, need to have precise control of their depth in the underwater environment. This is accomplished by achieving neutral buoyancy, a state of equilibrium where the positive and negative buoyancy forces acting on a diver under water are as close to equal as possible, allowing the diver to “hover” at their desired depth with little or no additional effort.
Effective buoyancy control is necessary for several reasons. First, proper buoyancy is necessary for safe and controlled ascents to the surface, the stage of a dive where a diver is most susceptible to pressure and decompression related injuries. Buoyancy control is also essential for maintaining and holding one's depth at safety and decompression stops (timed stops at specified depths to allow for absorbed gases to be released from a diver's body).
A diver without control over their buoyancy may collide with underwater hazards, which can result in the diver getting caught on, or injured by, these hazards. In addition, a diver who cannot control their buoyancy may cause damage to the underwater environment when they make contact with objects such as fragile coral reefs that take decades to develop and grow. Finally, a diver who maintains neutral buoyancy will not expend effort struggling to stay at a constant depth, thereby conserving their energy and reducing their air consumption.
Because the human body is in most cases positively buoyant, a diver usually needs to have additional negatively buoyant weight added to their diving equipment to reach a state of neutral buoyancy. Typically, this is done with lead weights either attached to a diving weight belt or by placing the weights inside of the weight pockets of a Buoyancy Compensator Device (BCD), an inflatable vest worn by divers.
As scuba equipment is added, removed or changed, the weight necessary to achieve neutral buoyancy changes. Scuba equipment may be positively or negatively buoyant, and the amount of buoyancy exhibited by an individual piece of equipment may change depending on several factors. Some of these factors are variable ones that change during the dive, such as depth and the air remaining in one's tank. A typical 80 cubic foot aluminum scuba tank when filled with air to 3000 PSI has a negative buoyancy of −1.4 lbs. When empty it has a positive buoyancy of +4.4 Lbs. When a diver descends to greater depths, the resulting pressure increase compresses a neoprene wetsuit, which reduces its buoyancy.
Other factors also change overall buoyancy. Once such example is the salinity of the water. Because salt water is denser than fresh water, additional weight is necessary to counter the increase in positive buoyancy when diving in salt water. An additional factor affecting a diver's buoyancy is whether the diver is wearing a wetsuit, and the thickness of the wetsuit. In warm tropical waters, a diver may not wear a wetsuit. In cooler waters, a diver may wear a 3 mm, 5 mm or even a 7 mm wetsuit. Each has significantly different positive buoyancy characteristics.
Because of the different conditions and equipment used for each type of dive, a diver has to change the amount of weight they use depending on the type of dive. A 200 pound diver that plans a dive for a warm freshwater lake without a wetsuit may only need 10 pounds of weight to maintain neutral buoyancy. That same diver in a 3 mm wetsuit in freshwater may require 14 pounds of weight to maintain neutral buoyancy. In saltwater with the same 3 mm wetsuit, the diver may require 18 pounds of weight to maintain neutral buoyancy.
In addition to overall weight, the placement of the weight on a diver effects the diver's orientation in the water. Ideally, a diver should maintain a flat trim in the water, wherein the orientation of their body is as close to horizontal as possible. With a diver's body in a horizontal position, the resistance in the water is reduced, thereby minimizing the amount of energy needed to swim. Also, if a diver does not maintain horizontal trim, the propulsion generated by the divers fins is directed partially upward or downward instead of horizontally, making it difficult to maintain the desired depth and causing the diver to expend additional energy to counter the upward or downward movement.
Modern BCDs contain several pockets in which weight can be added for buoyancy, as well as to aid in maintaining horizontal trim. Typically, a BCD will have removable (dumpable) weight pockets around the waist and non-dumpable weight near the shoulders. By placing weight in the pockets above and below the diver's horizontal center-of-gravity, a diver can adjust the amount of weight between these upper and lower pockets to help maintain horizontal trim.
Because the amount of weight necessary to maintain overall neutral buoyancy can vary, and the distribution of weight necessary to maintain horizontal trim when using BCDs with multiple pockets can also vary, being able to make precise weight adjustments in small increments can be advantageous in helping a diver be safe, comfortable and energy efficient underwater.
Scuba weights typically are made from cast lead and are manufactured in weight amounts typically between 1 and 5 pounds. They may be coated in rubber or plastic. Divers must buy or rent these weights in different configurations depending on the type of dive.
For divers using BCDs with multiple weight pockets, several different configurations may be necessary depending on the type of dive. In the example mentioned above, the diver in a 3 mm wetsuit diving in a freshwater requiring 14 pounds of weight to maintain neutral buoyancy may need to configure their overall weight using a 4 pound weight in each of their 2 dumpable weight pockets below their horizontal center-of-gravity and placing a 3 pound weight in each of their 2 non-dumpable weight pockets above their horizontal center-of-gravity. This allows for an overall total weight of 14 pounds and also spreads the weight out across the diver's body to maintain horizontal trim. If the diver decides to dive in the same freshwater lake when the water is warmer, they may decide to do so without a wetsuit. This may change the configuration to 10 pounds of overall weight with each of the 2 dumpable weight pockets containing 3 pound weights and the 2 non-dumpable pockets containing a 2 pound weight. Should the same diver choose to dive in the ocean wearing a 3 mm wetsuit, they may need 18 pounds of total weight, a pair of 5 pound weights in the dumpable pockets and a pair of 4 pound weights in the non-dumpable pockets.
For these 3 different examples, the diver would need a pair of 2 pound weights, a pair of 3 pound weights, a pair of 4 pound weights and a pair of 5 pound weights, for a total of 28 pounds, to achieve the various configurations needed for just the 3 examples given. Other factors may also change the required weight amounts, such as different equipment arrangements, wetsuits in 5 mm, 7 mm or greater thicknesses, the diver losing or gaining weight, etc. This may require a diver to purchase far more weight in total then they would ever need to achieve the different configurations necessary for any individual type of dives. This problem is even greater for diving operations such as retail dive shops, commercial diving companies and military dive units that must be able to configure weights for several people simultaneously taking part in diving classes, missions or trips.
While divers using weight belts would only be concerned about the overall weight used on the dive belt, any improvement to a weight system for BCD users must be compatible with those divers that prefer to use a weight belt.